Antiagers and polymers containing them

ABSTRACT

Compounds corresponding to the following general formula: ##STR1## wherein R 0  represents H or, together with R 1 , represents --CO-- when X represents --CO-- or, together with R 2 , represents --CO-- when X represents --CH 2  --CO, 
     a residue of R, R 1  and R 2 , H, C 1  -C 4  alkyl, aryl, COOR 5  or, when R 0  represents H and X represents --CO--, ##STR2##  and the other residues R, R 1  and R 2  represent H; R 3  represents H or CH 3  ; 
     R 4  represents C 7  -C 20  aralkyl; 
     R 5  represents H, C 1  -C 4  alkyl or C 6  -C 12  aryl; 
     X represents a residue --(CH 2 ) n  CO--, --(CH 2 ) n  SO 2 , --CH 2  --, --CH 2  O--CO-- ##STR3## m represents 1 or 2; and n represents 0 or 1; 
     are suitable for use as incorporable antiagers for polymers, particularly nitrile rubber.

This invention relates to compounds corresponding to the followinggeneral formula: ##STR4## wherein R⁰ represents H or, together with R¹,represents --CO-- when X represents --CO-- or, together with R²,represents --CO-- when X represents --CH₂ --CO,

a residue of R, R¹ and R², H, C₁ -C₄ alkyl, aryl, COOR⁵ or, when R⁰represents H and X represents --CO--, --CH₂ -- or --CH₂ --O--CO--,##STR5## and the other residues R, R¹ and R² represent H, X represents aresidue ##STR6## n represents 0 or 1; R³ represents H or CH₃ ;

R⁴ represents C₇ -C₂₀ aralkyl;

R⁵ represents H, C₁ -C₄ alkyl or C₆ -C₁₂ aryl; and

m represents 1 or 2;

and also polymers containing these compounds.

Polymers are rapidly changed by the action of light, air and heat andlose the favourable service properties thereof as a result ofdegradation and cross-linking processes. Because of this, antiagers areadded to the polymers, considerably prolonging the useful life thereof.However, an addition of antiagers is often not sufficient when utilityarticles of polymers of the type in question come into contact withmedia which are capable of extracting the antiagers and, hence,seriously impair or even neutralize the protective function thereof. Itis also known that antiagers migrate and exude from the polymers.

It has been proposed in such cases to bind the antiagers to the polymeror to use polymeric antiagers.

Thus, according to DE-OS 20 25 336, amides corresponding to thefollowing general formula: ##STR7## wherein R⁹ represents aryl;

R⁶ and R⁷ represent H or C₁ -C₄ alkyl;

R⁸ represents H, C₁ -C₄ alkyl, C₁ -C₄ alkoxy or C₁ -C₁₃ alkylamino;

R¹⁰ and R¹¹ represent a C₁ or C₂ alkyl or C₆ -C₁₀ aryl residue, acarboxyl or carboxyalkyl residue;

preferably acylamides of 4-aminodiphenylamine, are polymerized withbutadiene. Polymers of this type are said to show greater resistanceafter extractive treatments, such as dry cleaning, then polymers whichhave been stabilized solely by the addition of antiagers.

According to U.S. Pat. No. 3,867,334, the amides corresponding toformula (II) may also be used to stabilize carbon black-reinforced,sulphur-vulcanized rubber providing they are added under certainconditions.

DE-OS 25 09 654 describes the peroxidic grafting ofN-4-(phenylaminophenyl)-acrylamide: ##STR8## onto natural rubber.

DE-OS 30 22 952 relates to compounds corresponding to the followinggeneral formula: ##STR9## wherein R¹² represents H or CH₃ ;

R¹³ and R¹⁴ represent H, Cl, Br or C₁ -C₁₂ alkyl; and

A represents ##STR10## and rubber-like polymers which contain thesecompounds in chemically-bound form and which afford a certian, improvedprotection against ageing under extractive conditions.

Also DE-OS 31 13 351 recommends nitrile rubbers having a particularcomposition, including a content of from 5 to 60%, by weight, of a vinylchloride polymer, for heat-resistant and oil-resistant mouldings whichcontain, as stabilizers, compounds corresponding to formula (II) aboveor amides corresponding to formula (IV) below: ##STR11## wherein R¹⁵represents H or C₁ -C₄ alkyl;

R¹⁶ and R¹⁷ represent H, Cl, Br or C₁ -C₁₂ alkyl.

The requirements which the resistance of rubber components, for exampleseals and hoses, has to satisfy in the operation of internal combustionengines are becoming increasingly more stringent on account of thecompact construction involved and the elevated working temperatures. Inthis connection, it has been found that, although the antiageing effectof the known compounds reaches a useful level, it is still greatly inneed of improvement if damage and leaks attributable to oxidation are tobe avoided. In the event of normal ageing under non-extractiveconditions, it does not come anywhere near the effect of the non-fixableantiagers normally used, such as distyryl diphenylamine.

An object of the present invention is to provide new antiagers which maybe chemically fixed to polymers and which afford improved protectionagainst ageing under extractive conditions or in the presence ofoxidized oils or fuels and polymers containing these antiagers.

It has now surprisingly been found that the compounds of formula (I)mentioned initially afford the required improved protection againstageing. Preferred compounds (I) are those wherein

R⁰ represents H or, together with R¹, represents --CO-- when Xrepresents --CO--;

R represents H or CH₃ ;

R¹ represents H, CH₃, COOR⁵, ##STR12## R² represents H or CH₃ ; Xrepresents CO, CH₂, SO₂, CH₂ SO₂ or ##STR13## R³ represents H; R⁴represents C₇ -C₁₈ aralkyl;

R⁵ represents H or C₁ -C₄ alkyl; and

m represents 1 or 2.

Particularly preferred compounds (I) are those wherein

R⁰, R and R³ represent H;

R¹ represents H, phenyl or COOR⁵ ;

R² represents H or CH₃ ;

X represents CO or CH₂ ;

R⁴ represents C₇ -C₁₃ aralkyl;

R⁵ represents H or C₁ -C₄ alkyl; and

m represents 1 or 2.

The compounds corresponding to general formula (I) according to thepresent invention are produced by reacting 4-aminodiphenylaminederivatives corresponding to the following general formula: ##STR14##wherein R³, R⁴ and m are as defined above;

with compounds corresponding to the following general formula: ##STR15##wherein R, R¹, R² and X are as defined above; and

Y represents Cl or, together with R¹, represents --CO--O when Xrepresents --CO or, together with R², represents --CO-- when Xrepresents --CH₂ --CO or represents OR⁵ wherein R⁵ is as defined above.

The aralkyl group R⁴ is preferably in the p-position, although theproducts always contain a certain percentage of o-compound.

The production of the compounds (I) according to the present inventionby reacting the 4-aminodiphenylamine derivatives (V) with theunsaturated compounds (VI) may be carried out by various known methods,namely:

(1) by acylation of (V) with the reactive acid chlorides (for example(VI) with X=CO or SO₂ and Y=Cl) in the presence of bases, such as sodiumhydroxide, using the two-phase system according to Schotten-Baumann orin the presence of tertiary amines or alkali metal carbonates andcatalytic quantities of tertiary amines using the method described inU.S. Pat. No. 3,852,350 or in DE-OS 30 22 952;

(2) by aminolysis of esters (VI) (for example X=CO, Y=OCH₃ or o-phenyl)with amines (V), for example using alcoholates in accordance with J.Org. Chem. 28 (1963), pages 2915 or 2917;

(3) by ring-opening acylation of amines (V) with acid anhydrides (VI)(for example X=CO, Y+R¹ =OCO) in accordance with Ber. Deut. Chem. Ges.20, 3214, (1887);

(4) by ring closure of the semiamides (I) (for example R¹ =COOH, X=CO)obtained as in (3) under dehydrating conditions to form thecorresponding imides in accordance with L. H. Flett and W. H. Gardner:Maleic Anhydride Derivatives, John Wiley & Sons, 1952, pages 106 etseq., and Houben-Weyl, Methoden der organ. Chem. Vol 11/2, pages 16 etseq., 4th Edition, 1958,

(5) by alkylation of amines (V) with alkylating agents (VI) (for exampleX=Cl or X= ##STR16## in accordance with DE-SO 30 22 952.

The new antiagers obtainable by these methods may be purified byrecrystallization and, optionally, by the addition of absorbents, suchas active carbon or active aluminas. In many cases, however, they areused as crude products.

The new antiagers corresponding to general formula (I) may be fixed topolymers in many ways, i.e. during radical polymerization of themonomers mentioned below, preferably by grafting onto preformedpolymers, but especially during hardening and vulcanization of thepolymers.

These reactions are carried out in known manner in the presence ofcompounds (I) in mass, emulsion, solution or dispersion, while hardeningor vulcanization is carried out under the conventional conditions in thepresence of known hardening and vulcanization systems. The antiagers areused in a quantity of from 0.2 to 10%, by weight, preferably from 0.5 to5%, by weight, based on the polymer.

The antiagers corresponding to general formula (I) according to thepresent invention may also be reacted in known manner with vinylmonomers to form copolymers having molecular weights of from 1000 to30,000 and an increased content of from 5 to 70%, by weight, preferablyfrom 10 to 60%, by weight, of (I).

In addition, the antiagers (I) may also be grafted onto polymers havingmolecular weights of from 1000 to 30,000 (number average), preferablyfrom 2000 to 20,000, so that the polymers contain from 10 to 60%, byweight, preferably from 10 to 50%, by weight, of bound antiager. Suchcompounds are then added to the high molecular weight polymers andlikewise form migration-resistant and substantially non-extractable,effective polymeric antiagers. They are added to the high molecularweight polymers in such quantities that the above-mentionedconcentrations of antiager are obtained in the polymer as a whole. Tothis end, the relatively low molecular weight polymers containing theantiagers in bound form are used in quantities of from 1 to 25%, byweight, preferably from 4 to 20%, by weight, based on the high molecularweight polymers.

Suitable low molecular weight polymers for grafting reactions of thetype in question are, for example, polybutadienes, polyisoprenes,copolymers of butadiene and/or isoprene with styrene, acrylonitrile,methyl methacrylate, ethyl acrylate, α-methyl styrene, piperylene,1,3-hexadiene, ethylene, propylene and vinyl acetate.

Suitable vinyl monomers for producing the copolymers are those mentionedabove.

The grafting of the antiagers onto the polymers is carried out underradical conditions, for example in the presence of known radicalinitiators, such as t-butyl perpivalate, dicumyl peroxide, di-t-butylperoxide or azodiisobutyronitrile, undiluted or in inert solvents, suchas toluene, xylene, petrol, chlorobenzene or dichlorobenzene, attemperatures of from 50° to 200° C., preferably from 70° to 180° C.

The new antiagers are suitable for a wide range of rubbers and plastics,but especially rubbers for example for polymers of 1,3-dienes, such asbutadiene, isoprene, piperylene, 2-chlorobutadiene, 2-ethyl-butadiene,and copolymers thereof with vinyl monomers, such as styrene, p-methylstyrene, α-methyl-styrene, norbornene, norbornadiene, acrylic acid,acrylic acid esters and amides, acrylonitrile, ethylene, propylene andvinyl acetate, for polyalkenamers, for example of cyclopentene or1,5-cyclooctadiene, and for polymers of 1-olefin mixtures, for exampleof ethylene-propylene or ethylene/propylene/diene containing isolateddouble bonds. Such polymers may have been formed by radical,coordinative, metathetic or ionic polymerization.

Examples of polymers of the type in question are, for example, BR,natural rubber, SBR, NBR, EPDM and CR, polypentenamer, alsopolyethylene, polypropylene or polystyrene with small contents of doublebonds, and finally single-phase or multiphase polymer mixtures, such asABS or polystyrene, polyethylene, polypropylene, but especially polymerscontaining double bonds.

The antiagers are particularly effective in nitrile rubber.

The rubbers may be vulcanized.

A further improvement in breaking elongation may be obtained by theaddition of from 5 to 15%, by weight, based on rubber solids, ofoligomeric thioethers, for example ether thioethers, such as Vulkanol85®, a product of Bayer AG Leverkusen.

SYNTHESIS OF THE AMINES (V) EXAMPLE 1 ##STR17##

216 g (2 moles) of benzyl alcohol were added dropwise with stirringunder nitrogen over a period of 1 hour at 200° C. to a mixture of 184 g(1.0 mole) of 4-aminodiphenylamine and 20 g of acid-activated Fuller'searth. After 3 h at 200° C. followed by dilution with toluene, thereaction mixture is filtered through a pressure filter, the filtrate isconcentrated by evaporation and unreacted starting products aredistilled under reduced pressure. 280 g of a fraction which, in additionto the benzyl-substituted 4-aminodiphenylamine, contained smallquantities of the dibenzyl-substituted compound, finally distilled overat 230°-260° C./0.6-1.0 mbar.

EXAMPLE 2 ##STR18##

208 g (2.0 moles) of styrene were added dropwise with stirring undernitrogen over a period of 2 h at 200° C. to a mixture of 184 g (1.0mole) of 4-aminodiphenylamine and 20 g of acid-activated Fuller's earth.After 1 h at 200° C., followed by dilution with toluene, the reactionmixture was filtered through a pressure filter, the filtrate wasdistilled under reduced pressure and then freed from solvent andunreacted starting products. 286 g of the target compound finallydistilled over at 220°-243° C./0.2-0.3 mbar.

EXAMPLE 3 ##STR19##

1025 g (8.7 moles) of α-methyl styrene were added dropwise with stirringunder nitrogen over a period of 2 h at 200° C. to a mixture of 800 g(4.35 moles) of 4-aminodiphenylamine and 80 g of acid-activated Fuller'searth. After 1 h at 200° C., the reaction mixture diluted with toluenewas filtered through a pressure filter and the filtrate distilled underreduced pressure, solvent and unreacted starting products distillingover first, followed at 236°-255° C./0.3 mbar by a fraction I (787 g)which consisted essentially of monoalkylated compounds and then, at268°-288° C./0.3-0.5 mbar, by a fraction II (530 g) which consistedessentially of the dialkylated compound.

EXAMPLE 4

The procedure was as in Example 3, except that the crude reactionproduct was not subjected to fractional distillation after theseparation of unreacted starting products, but instead was used withoutfurther purification.

SYNTHESIS OF THE ANTIAGERS (I) EXAMPLE 5 ##STR20##

147 g (0.47 mole) of fraction I from Example 3 were dissolved in 500 mlof xylene. 74.4 g of anhydrous sodium carbonate and 1 g of triethylaminewere then added, the resulting suspension stirred for approx. 1 h/40° C.and 54 g (0.52 mole) of methacrylic acid chloride which had beendissolved in approx. 50 ml of xylene were added dropwise over a periodof from 30 to 40' at 20° C. After 2 h at from 20° to 30° C., thereaction mixture was heated at from 45° to 50° C. for from 2 to 3 h,extracted with water and the organic phase concentrated by evaporationunder reduced pressure after drying. The residue comprised 178 g, M.p.105°-106° C. (toluene/petroleum ether). The NMR-spectrum agrees with theabove structure.

EXAMPLE 6 ##STR21##

151 g (0.5 mole) of fraction I from Example 3 were dissolved in from 800to 900 ml of toluene and 49 g (0.5 mole) of maleic acid anhydridedissolved in 200 ml of toluene added dropwise to the resulting solutionover a period of 2 h at from 35° to 40° C. The suspension was thenstirred for another 2 h at 40° C., filtered under suction, the crystalswashed with toluene and petroleum ether and then dried.

Yield: 186 g, M.p.: 179°-181° C. The NMR spectrum agrees with the abovestructure.

EXAMPLE 7 ##STR22##

35 g (0.25 mole ) of allylsulfonic acid chloride were added to a mixtureof 78 g (0.25 mole) of fraction I from Ex. 3, 25 g (0.25 mole) oftriethylamine and 200 ml of toluene under nitrogen during two hours at50° to 60° C. under stirring. After one further hour at 50° to 60° C.the precipitate was filtered off and washed with toluene. The cominedfiltrates were washed with water, dried and concentrated by evaporationunder reduced pressure.

The residue comprised 99 g of viscous brown liquid, which according tothe NMR-spectrum corresponds to the above formula.

EXAMPLE 8 ##STR23##

151 g (0.5 mole) of fraction I from Example 3 were dissolved in 300 mlof toluene. 60 g (0.5 mole) of chloroformic acid allyl ester and 22 g(0.55 mole) of sodium hydroxide in 50 ml of water were added during 60to 70 minutes at 20° to 25° C. under nitrogen and stirring from separatedropping funnels. The mixture was stirred for further 2 to 3 hours at20° to 25° C. and then diluted with water.

The organic phase was separated, washed with water several times, driedand concentrated by evaporation. The residue comprised 193 g of a darkresin, which according to elemental analysis and the NMR spectrumcorresponds to the above formula.

EXAMPLE 9 ##STR24##

151 g (0.5 mole) of fraction I from Example 3 were mixed with 200 ml ofpropylene glycol. During 1 to 2 hours 38 g (0.5 mole) of allyl chlorideand 20 g (0.5 mole) of sodium hydroxide in 200 ml water were addeddropwise and simultaneously from different dropping funnels understirring and nitrogen at 100° C.

After one further hour of stirring at 100° C. the main amount of thesolvent was distilled of under reduced pressure, water and toluene wereadded and the phases were separated. The organic phase was washedseveral times with water, dried and concentrated under reduced pressure.

The residue comprised 169 g of a dark resin, which according to theelemental analysis and NMR spectrum agrees with the above structure.

EXAMPLE 10 ##STR25##

84 g (0.5 mole) of cinnamic acid chloride were reacted instead ofchloroformic acid ally ester as in Example 8. After dilution with waterthe precipitate was filtered off washed several times with water andtoluene and dried. 147 g of yellow crystalls were obtained with amelting point of 184° to 186° C. The elemental analysis corresponds withthe above formula.

COMPARISON EXAMPLE 1 ##STR26##

92 g (0.5 mole) of 4-aminodiphenylamine were reacted with methacrylicacid chloride as in Example 5.

Yield 95 g,

M.p. 98°-101° C.

APPLICATION EXAMPLES EXAMPLE 11

An NBR rubber of 72%, by weight, of butadiene and 28%, by weight, ofacrylonitrile was vulcanized using the following formulation in thepresence of antiagers according to the present invention and knownantiagers:

100.0 parts, by weight, of NBR

1.5 parts, by weight, of mercaptosilane

30.0 parts, by weight, of precipitated silica

0.75 parts, by weight, of stearic acid

3.0 parts, by weight, of zinc oxide

2.5 parts, by weight, of a mixture of fatty acid and fatty acid esters

30.0 parts, by weight, of calcined kaolin

0.25 parts, by weight, of sulphur granulate, 80%

2.5 parts, by weight, of tetramethyl thiuram disulphide

2.0 parts, by weight, of dibenzothiazyl disulphide

4.0 parts, by weight, of mercaptobenzthiazole, zinc salt

10.0 parts, by weight, of a thioether

1.5 parts, by weight, of antiager A-C

A=product of Comparison Example 1

B=product of Example 5

C=distyryl diphenylamine

    ______________________________________                                                       A       B       C                                              ______________________________________                                        Mooney scorch 120° C.                                                                   16.0      15.5    16.5                                       (mins.)                                                                       Vulcameter t.sub.10 (mins.)                                                                    2.4       2.4     2.4                                        170° C. t.sub.10 (mins.)                                                                3.6       3.4     3.5                                        Vulcanization 20' 170° C.,                                             standard bar II                                                               Tensile strength (MPa)                                                                         18.8      17.5    19.4                                       Breaking elongation %                                                                          580.0     565.0   595.0                                      Hardness, RT, Shore A                                                                          60.0      59.0    59.0                                       Hot air ageing at 150° C.,                                             cellular furnace                                                              Residual breaking elongation,                                                                  90.0      100.0   97.0                                       %, after 3 days                                                               Residual breaking elongation,                                                                  62.0      70.0    67.0                                       %, after 5 days                                                               Ageing in fuel C,                                                             48 h/40° C., redrying in vacuo                                         48 h/40° C.                                                            Hot air ageing at 135° C.,                                             cellular furnace                                                              Residual breaking elongation,                                                                  66.0      75.0    10.0                                       %, after 7 days                                                               Residual breaking elongation,                                                                  53.0      62.0    2.0                                        %, after 11 days                                                              ______________________________________                                    

It follows from the measurements that

(1) antiager A, corresponding to U.S. Pat. No. 3,876,334, is lesseffective than the conventional commercial antiager C againstconventional hot-air ageing without extraction and

(2) is less effective than the antiager B against conventional hot-airageing and against ageing after extraction and

(3) that antiager B is superior to the conventional product C, evenagainst conventional hot-air ageing without extraction.

We claim:
 1. Compounds corresponding to the formula ##STR27## wherein R¹is hydrogen, methyl or --COOR⁵ ;R² is hydrogen or methyl; R³ is hydrogenor methyl; R⁴ is aralkyl having 7 to 20 carbon atoms; R⁵ is hydrogen oralkyl having 1 to 4 carbon atoms; and m is 1 or
 2. 2. Compoundsaccording to claim 1 wherein R⁴ is ##STR28##
 3. Compounds according toclaim 1wherein R¹ is hydrogen; R² is methyl; R³ is hydrogen; and R⁴ is##STR29##
 4. Nitrile rubbers and nitrile rubber vulcanizates containingfrom 0.2 to 10%, by weight, of the compounds according to claim
 1. 5. Acopolymer having a molecular weight of from 1,000 to 30,000 and derivedfrom a mixture of copolymerized vinyl monomers containing 5 to 70% byweight of a compound of the formula ##STR30## wherein R¹ is hydrogen,methyl or --COOR⁵ ;R² is hydrogen or methyl; R³ is hydrogen or methyl;R⁴ is aralkyl having 7 to 20 carbon atoms; R⁵ is hydrogen or alkylhaving 1 to 4 carbon atoms; and m is 1 or
 2. 6. A graft polymerconprising 10 to 60% by weight of antiager compound grafted onto apolymer derived from olefinic monomers and having a molecular weight of1000 to 30,000 wherein said antiager compound is of the formula##STR31## wherein R¹ is hydrogen, methyl or --COOR⁵ ;R² is hydrogen ormethyl; R³ is hydrogen or methyl; R⁴ is aralkyl having 7 to 20 carbonatoms; R⁵ is hydrogen or alkyl having 1 to 4 carbon atoms; and m is 1 or2.